aMule has a very nice preview option for transferred files, but it only allows preview on certain file extensions. It would be nice to be able to customize the extension list to add new extensions if the configured preview application can support them (it would be up to the user to make that determination).

For example, .flv (flash video) files can be viewed successfully by mplayer (the default preview application under Linux), however aMule doesn't recognize .flv files as something that can be previewed. If the list of accepted extensions could be user updated, then a new build of aMule wouldn't need to be released just to support this new extension.